A simulation approach to modelling quality and reliability features of plant processes

The relationship between component and system reliability is a key factor in the improvement of plant processes and a wide variety of models have been studied, under the general headings of “Probabilistic Methods”, “Graph Theoretical Methods” and “Simulation”. An outline review of these reliability models is given as a background to the work of the thesis and the ideas were used to steer the design of the software tool, which we have developed. The tool is generic in the sense that it can be used for any production system consisting of any number of parallel production lines, although we have considered its application in detail for one system only. In particular, we describe an application of reliability theory in the modelling of a plant process, which incorporates examples of Load-Sharing, parallel and series stages and we demonstrate how the production plannmg control is related to reliability considerations. The tool has been tested in reference to a real production system, for which Quality and Reliability features have been analysed though data collection and simulation. The production system is located in Intel’s ESSM (European Site for System Manufacturmg) plant m Ireland. The plant's products are the basic components of a Pentium II processor, based on a new technology, (known as MMX or Secc), which enables enhancements for multimedia and communication applications. We have also applied our software tool to the old production line (pre-datmg Secc Technology), both for calibration purposes and to compare the two lines Software features mclude the ability to, mvestigate line reaction to changes in quality and reliability, to pmpomt problem areas, to cost failures in reliability, to explore degraded operation, stages with poor quality/reliability can be identified and Estimate the real UPH (Units Per Hour). We present an analysis of system performance and provide recommendations for possible improvements to the system

Epidemiological evaluation of subclinical mastitis of dairy cows in Greece

ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗSubclinical mastitis, diagnosed by elevated somatic cell count (SCC) in milk, is an important monitoring parameter of dairy cows’ udder health, related to their productivity and welfare. The present retrospective study aims to evaluate the epidemiology of subclinical mastitis (SCM) among the 37 herds of the Holstein Association of Greece participating in the milk quality recording system “ΙΩ”, from the start of 2015 until the end of 2018. The herds’ inclusion criterion was the consistency of monthly SCC recording throughout at least one full year between 2015 and 2018, with a maximum interval of 61 days between two consecutive monthly SCC recordings. Twenty-six herds (8630 cows) in 2015, thirty herds (10763 cows) in 2016, thirty herds (10945 cows) in 2017 and twenty-six herds (9597 cows) in 2018 were included. The prevalence of SCM and chronic SCM, the incidence rate of new cases of SCM, as well as the average somatic cell score and bulk tank milk SCC were determined for each of the four years. The results indicate a progressive deterioration of udder health from the onset of the cow’s productive life until culling. A year-over-year increase in the number of cows with subclinical mastitis led to an overall SCM prevalence of 34.5%, chronic SCM prevalence of 26.9% and a bulk tank milk SCC of 463000 cells/mL, in 2018. The average somatic cell score, a base 2logarithm of individual cow’s SCC, was found persistently above the subclinical mastitis indicative cut-off in all four years, with a peak in 2018. At herd level, the incidence rate of new SCM cases was 12 new cases / 100 cows / month; the highest incidence rate was observed in the early lactation stage group (1-60 days-in-milk), in all four years, reaching a peak of 31 new cases / 100 cows / month, in 2018. In 2018, prevalence of heifers’ SCM and chronic SCM was23.4% and 16.9%, respectively. Despite the adequate average 305-days milk yield (9608 kg in 2018), the results were indicative of poor udder health status, pointed out by reduced duration of cows’ productive life (less than 3 lactations)and lower milk quality (elevated SCC). The severity and wide spreading of subclinical mastitis in Greek dairy herds highlights the necessity of a national mastitis control program, aiming to improve the productive efficacy, management decisions accuracy and quality of produced milk

Photodynamic therapy of choroidal neovascularization with enlargement of the spot size to include the feeding complex

This is a case report of a 83-year-old man with choroidal neovascularization (CNV), due to age-related macular degeneration (AMD) in his right eye. Digital fluorescein (FA) and indocyanine green angiography (ICG) were performed, which disclosed predominantly classic subfoveal CNV and a dilated and tortuous feeding complex. The visual acuity was 20/800. Anti-vascular endothelial growth factor (anti-VEGF) treatment was suggested, however, the patient was not keen to receive an intraocular injection. Modified photodynamic therapy (PDT) with spot size enlarged, to include not only the CNV lesion but the feeding complex as well, was performed. Ten days after one session of PDT, ICG showed absence of leakage from the CNV and complete occlusion of the feeding complex. The visual acuity gradually improved to 20/100 and remained stable during the following 23 months. No evidence of CNV leakage was seen in the FA and ICG during the follow up period. Adjustment of the PDT spot size to include the detectable by ICG feeding complex might be an additional option in order to close the subfoveal CNV and might be considered as an alternative to intravitreal injection of anti-VEGF in selected cases where anti-VEGF treatment is not available